Grinding machine



March 23; 1943. a c. HU NT GRINDING MACHINE Filed Dec. 6, 1941 W 7. ;W M f C. r m r q M wnwaawow to rotate about their respective axes.

Patented Mar. 23,1943

UNITED STATES PATENT rates GRINDDIG MACHINE Grover C. Hunt, Carlisle, Pa. Application December 6, 1941, Serial No. 422,001

6 Claims. (01. 51-161) This invention relates to grinding machines of the type generally known as lapping machines and, more specifically, relates tolapping machines which are particularly intended for the grinding of polygonal, relatively thin devices or articles such as piezo-electric crystals.

It has heretofore been prposed,'and is now known, to provide a lapping machine in which externally geared work holders are disposed between two superposed abrasive discs and are geared to a rotating pinion which is located centrally of the discs and to a fixed outer ring gear which is concentric with the pinion, whereby rotation of either, the pinion or the ring gear will cause the work holders to describe a planetary movement about the pinion and, simultaneously,

The articles carried by the'work holders are thus caused to move in either an epicycloidal or a hypocycloidal path across the faces of the discs. It is also known to so proportion the dimensions of the discs and the work holders that during their travel the articles carried by the work holders are caused to pass beyond the inner and outer peripheral edges of the discs, thereby causing travel of the articles over the entire surfaces of the discs.

I have found that in the operation of machines such as that described the movement of part of the work piece beyond the inner or outer peripheral edge of the discs permits the work holder, which also extends beyond the edge of the discs, to be deformed to a position below or above the lower or upper surface, respectively, of the work piece, whereby the edge of the holder may move below the lower surface or above the upper surface of t. work piece upon further movement of the holder in its planetary and rotary travel. This has been found to occur particularlly in the grinding of thin articles, such as piezo-electric crystals, in which a relatively thin and flexible holder is employed. It has been found that such a clisarrangement of the holder and work piece results in the ruining of the holder and the work piece.

It is therefore an object of the invention to provide means, in a machine of the type described and in which the work pieces being ground move radially beyond theinner and outer peripheries of the discs, to prevent the work holders from engaging or passing above or below the upper or lower surfaces of the work pieces.

It is also an object of the invention to provide a machine which is particularly useful and adgrinding piezo-electrie crystals.

Means for eifecting these objects, as well as other objects of the invention, will be made ap parent by the following description and th annexed drawing, it being understood that the de scription and drawing are only illustrative of the invention, for the limits of which reference must be had to the appended claims.

Referring to the drawing, in which the same reference numerals and letters refer to like parts,

Fig. 1 is a vertical sectional view bf a machine embodying this invention, taken on line l-l of Fig. 2;

Fig. 2 is a plan view of the machine of Fig. 1, taken on the line 2--2 of Fig. l, and

Fig. 3 is a view of a part of the machine of Figs. 1 and 2, taken on the line 3-3 of Fig. 2.

A machin embodying the features of my invention is disclosed in the various figures of the drawing and comprises a base or standard 2 which supports a lower abrasive disc 4 which is fixed against movement, as by rigid attachment to the base. The lower disc is provided with a preferably circular central opening within which is disposed a pinion gear 6 which may be driven by any suitable means such as the pulley and belt 8. The gear 6 extends substantially above the upper surface of the lower disc. Concentric with pinion 6 and surrounding the disc 4 is a ring gear l0 having teeth l2, It on its internal and' external faces respectively. 7 The ring gear it is mounted for rotation and is supported by bearbe driven by suitable means such as the pulley and belt arrangement 22. An upper abrasive disc 30, which is substantially identical with the lower disc is attached to a cover 32 and is adapted to be received'within the ring gear, whereby the abrasive faces of the two discs are opposed and will be in engagement with each other unless the crystals or the work holding means which are described hereinafter ar interposed between them. The cover 32 and the upper disc are provided with openings within which a fixed pin, such as 36, may be received in order to prevent rotary or other movement of the upper disc. The cover may also be provided with handles 38 whereby it and theattached upper disc may be lifted. The upper disc and the cover therefor ar preferably provided with a central opening which receives the upper portion of the pinion gear 6. vided circular work holders 50, each of which is provided with gear teeth on its external periphery and is of such size that the gear teeth thereon engage those on the pinion gear 6 and the internal teeth l2 of the ring gear l0. Openings 52 are provided in each work holder within each of which a crystal is received and held during movement of the work holders.

The discs and the work holders are so proportioned that crystals carried by the work holders are caused to move beyond the inner and outer peripheries of the discs during their travel. Means are provided by the invention for preventing that portion of the holder which extends inwardly or outwardly of the inner or outer periphery of the discs from passing above 'or below that portion of any crystal held by the holder which also protrudes beyond such peripheries. 62 which are attached to the lower and upper discs, respectively, and which tightly but preferably movably surround their respective discs, and the rings 68, Ill which are attached to the lower and upper discs, respectively, within the central openings therein. According to the invention, the rings 60 and 68 are so attached to the lower disc that their upper surfaces 54 are spaced below the abrasive surface of the lower disc by a distance which is less than the thickof the work holder 50 which is being used at any time. The rings 52 and W are so attached to the upper disc that their lower faces 86 are spaced above the abrasive surface of the upper disc by a distance which is less than the thickness of the work holder 50. By reason of their movable connection to the respective discs the positions of the rings may be adjusted as the discs wear.

It will be seen that if the part of a work holder which protrudes beyond the inner or outer Between the two abrasive discs are pro- Such means comprise the rings 60,

peripheral edge of the discs is deformed, for example as shown in broken lines in Fig. 3, it cannot deform as much as 'its own thickness by reason of the ring 60 r 6B and, therefore, cannot deform or bend sufficiently, to pass below the lower surface of the crystal. -If, for any reason,'the work holder should be deformed upwardly instead of downwardly the ring 5201' HI would act in the same manner to preventthe protruding part of the work holder from pass-' ing above the upper surface of the crystal.

While l have described my invention with reference to the grinding of crystals, it will be understood that the invention is of general application and is not limited to the grinding of any particular materials or devices. It will also be understood that whileI have described my inventionwith reference to a machine having f fixed, horizontal, vertically-spaced abrasives, it may, without departing in any way from the ,invention, be applied to other types and constructions of grinding machines.

Although only one form of the invention is illustrated and described in this application, it

will be understood by those skilled in theart that modifications and improvements may be made without departing in any way from the spirit or scope of the invention, for the limits of which reference must be had to the appended claims. I .I-

I claim:

1. A lapping machine comprising upper and lower abrasive discs, a plurality of work holders" within the central opening therein; face of which adjacentand parallel ing face ,of the abrasive disc to which-it is at-. I tached being spaced from suchlworking face thickness of the 7 disposed between the discs and arranged in a seriesabout the common center thereof and each having at least one opening therethrough within which a work piece is adapted to be held, means for causing planetary movement or said work holders about the common center of the discs and rotary movement about their individual axes whereby work pieces held by the work holders will be moved radially and circumferentially over the discs,-the dimensions of the discs and of the work holders being such that in its outermost position of radial movement a. part of each work piece passes beyond the outer perlphery of the discs, and means for preventing the work holder from passing under or over the work piece held thereby as parts of the work holder and work piece extend beyond the perlphery of the discs, said means comprising a ring attached to and surrounding at least one of said discs, the annular face of each ring adjacent and parallel to the working face of the disc to which it is attached being spaced from such working face by a distance less than the thickness of the work holder which is being used.

2. A lapping machine comprising upper and lower abrasive discs having registering central openings therein, a plurality of work holders disposed between the discs and arranged in a series about the common center thereof and each having at least one opening therethrough within which a work piece is adapted to be held, means for causing planetary movement of said work holders about the common center of the discs and rotary movement about their individual axes whereby work pieces held by the work holders will move radially and circumferentially over the discs, the dimensions of the discs and of the work holders being such that in its innermost position of radial movement a part of, each work piece passes beyond the inner periphery of the discs, and a ring'attached'to the inner periphery of at least one the, .annular bya distance less than the work holder. i a

3. A lapping machine comprising upper and lower abrasive discs having registering central openings therein, a plurality of'worls holders disposed between the discs and arranged in a series about the commoncenter thereof and each having at least one opening therethrough within which a work piece is adapted to be held, means 'for causing planetary movement of said work holders about the common center of the discs and rotary movement about their individual axes whereby work pieces held by the work holders will move radially and circumferentially over the discs, the dimensions of the discs and of the work holders being such that in its innermost and outermost positions of radial movement a part I of each article passes beyond the inner and outer peripheries of the discs, and means for holding I l the part of the work holder which extends beyond eitherperiphery of the discs within a, space between the upper and lower faces of a work piece -held thereby, said means comprising a ring attached to and surrounding each of said discs and a ring attached to each disc within the central opening therein, the upper surface of each 'ringsattached to the lower disc being spaced below the upper surface of the lower disc by a distance less than the thickness of the work holder of said discs,

to ltheworkand the lower surface of each ring attached to the upper disc being spaced above the lower sur- -face of the upper disc by a distance less than the thickness of the work holder. v

'4. A lapping machine comprising upper and lower abrasive discs, a plurality of work holders disposed between the discs and arranged in' a series about the common center thereof and each.

holders willrbe moved radially and circumferem tially over the discs, the dimensions of the discs and of the work holders being such that in its ,outermostposition of radial movement a part of each work piece passes beyond the outer periphery of the discs, and a ring surrounding and mounted on at least one of the discs for adjusting movement toward and away from the work ing face thereof.

5. A lapping machine comprising upper and lower abrasive discs having registering central openings therein, a plurality of work holders disposed between the discs and arranged in a, series about the common center thereof and each having at least one opening therethrough within which a work piece is adapted to be held, means for causing planetary movement of said work holders about the common center of the discs and rotary movement about their individual axes whereby work pieces held by the work holders will move radially and circumferentially over the discs, the dimensions of the discs and of the work holders being such that in its innermost position of radial movement a part or each work I piece passes beyond the inner periphery of the discs, and a ring mounted on the inner periphery of at least one of said discs within the central opening therein for adjusting movement towardand away from the working face thereof.

6. A lapping machine comprising upper and lower abrasive discs having registering central openings therein, a plurality of work holders disposed between the discs and arranged in a series about the common center thereof and each hav-. ing at least one opening therethrough within which a, piece is adapted to be held, means for causing planetary movement of said work holders. about the common center of the discs and rotary movement about their individual axes whereby work pieces held by the work holders will move radially and circumferentially over the discs, the dimensions 01' the discs and of the work holders being such that in its innermost and outermost position of radial movement a part 01' each work piece passes beyond the inner. and

outer peripheries of the discs, and means for holding the part of the work holder which xtends beyond either periphery of the discs with in a space between the upper and lower faces of a work piece held thereby, said means comprising a. ring attached to and surrounding each of said discs and a ring attached to each disc within the central opening therein.

' GROVER C. HUNT. 

